1. Field of the Invention
This invention pertains to liquid crystal optical image attenuators.
Most particularly the invention relates to an optical image attenuator utilizing one or more liquid crystal layers which scatter the directed light when an electrical potential is applied to the layer.
2. Description of the Prior Art
Prior art variable optical attenuators such as iris diaphragms are limited to an attenuation range of about 200:1.
U.S. Pat. No. 1,770,535 to Sukumlyn discloses a variable light refractor in which the refraction is varied by varying voltage applied to a transparent electrolyte and dielectric medium, and in which further refraction can be obtained through the use of multiple stages of the device. U.S. Pat. No. 2,915,943 to Brown et al. discloses a system similar to Sukumlyn but in which the dielectric medium is placed between the two electrodes. U.S. Pat. No. 3,752,897 to Bousky discloses an optical modulator that employs a liquid crystal with electrically controlled refraction and with dissipative materials for dissipating acoustic and extraneous scattered light energies. U.S. Pat. No. 3,622,226 to Matthies discloses a linear array of liquid crystal cells, with transparent electrodes and extraneouslight-absorbing material on its sides. U.S. Pat. No. 3,697,289 to Goldstein discloses a crystal light modulator wherein both aperture and light intensity control is effected.
A discussion of chemical compounds suitable for liquid crystal layers and transparent electrodes usable therewith is contained in U.S. Pat. 3,499,112 issued to G. H. Heilmeier et al. issued Mar. 3, 1970.